Various parenteral liquids are administered to a patient under a positive pressure through an administration set. The positive pressure may be generated by gravity flow or by an appropriate pump. It is often necessary or desirable to monitor the pressure under which the fluids are delivered to the patient. This can be accomplished, for example, with a diaphragm or membrane type pressure sensor and a pressure transducer.
One problem with the sensing of pressure in an administration set is that the pressure sensor should not be allowed to trap any gas or bubbles that may exist in the liquid. If bubbles were trapped and, subsequently released and infused into the cardiovascular system of the patient, the results could be fatal to the patient.
One technique for pressure monitoring is to place a diaphragm over the top of an elongated channel through which the liquid flows and devices of this type are shown, for example, in German Pat. No. 888,933 and Cunningham et al U.S. Pat. No. 4,398,542. According to Cunningham et al, this approach does not trap air in the pressure sensor.
Another approach, which is structurally simpler, is to simply tap into the conduit of the administration set using a Tee to couple the pressure sensor to the conduit. However, this approach makes it difficult to purge air from the system and creates a likelihood of air entrapment in the Tee connection or in the pressure sensor.